I think the correct answer would be old and metal poor stars are found in the galactic nucleus. This nucleus us a region in the center of a galaxy which contains a higher luminosity than other parts. It produces very high amounts of energy. Hope this helps.
To solve this problem we will apply the concept of centripetal acceleration. This type of acceleration is described as the product between the square of the angular velocity and the turning radius. Mathematically the expression can be expressed as

Here,
Angular velocity
r = Radius
Our values are given as,


Replacing,


Therefore the electron's centripetal acceleration is 
I would think the answer is c.
Total energy =kinetic energy +potential energy
Change in energy =change in (kinetic energy +potential energy)
potential energy, 
where m is the mass, g is acceleration due to gravity and h is the height.
potential energy per unit mass =gh
change in potential energy per unit mass = 
where, h is the height.
kinetic energy= 
change in kinetic energy per unit mass,
In the given question:
Height varies from 90 m to zero as river flows from 90 m height to lake at 0 m
Velocity varies from 3m/s at top to o m/s at bottom.
Therefore,

Here, it was mentioned in the question internal energy of the water is constant and there is no change in the pressure at the inlet and outlet.